1. Field of the Invention
The present invention relates to a temperature measuring method, a storage medium, and a program, which can measure a temperature of an object to be measured (for example, a semiconductor wafer or a liquid crystal substrate) in a non-contact manner.
2. Description of the Related Art
Accurately measuring a temperature of a substrate (for example, a semiconductor wafer) to be processed by using a substrate processing apparatus is very important in order to accurately control shapes, properties, and so on of films or holes formed on or in the semiconductor wafer by various processes such as film formation and etching. Accordingly, a temperature of a semiconductor wafer has been measured by using various conventional methods such as a temperature measuring method using a resistance thermometer, a fluorescent thermometer for measuring a temperature of a rear surface of a base, or the like.
Recently, a temperature measuring technology using a low-coherence interferometer which can directly measure a temperature of a semiconductor wafer, which is difficult to measure by conventional temperature measuring methods, has been developed. Also, as the temperature measuring technology using the low-coherence interferometer, a technology has been suggested in which a light from a light source is divided into a measurement light for temperature measurement and a reference light by a first splitter, the measurement light is divided into n measurement lights by a second splitter, the n measurement lights are emitted to n measurement points, and interference between reflected lights of the n measurement lights and a reflected light of the reference light reflected by a reference light reflecting unit is measured to simultaneously measure temperatures of the plurality of n measurement points (refer to, for example, Patent Reference 1). According to this technology, a light from a light source is emitted to an object to be measured, an optical path length from a surface to a rear surface of the object is obtained from an interference wave between a reflected light from the surface of the object and a reflected light of a reference light, and from an interference wave between a reflected light from the rear surface of the object and the reflected light of the reference light, and a temperature of the object is calculated from the obtained optical path length.
However, if a thin film having a thickness less than or equal to a coherence length of the light source is deposited on the object, the optical path length of the interference waves may be misaligned due to overlapping of the interference waves by multiple reflection of the measurement light in the thin film. Accordingly, the optical path length from the surface to the rear surface of the object cannot be accurately calculated, and the temperature of the object cannot be accurately monitored.
(Patent Reference 1) Japanese Laid-Open Patent Publication No. 2006-112826